Ozone Treatment for Pharmaceutical Residues
About 100,000 diverse chemicals are registered in the European Union (EU). Out of these 100,000, about 30,000 are distributed in large quantities, where each one is distributed in quantities of about one ton per year or more for human health consumption. During production, disposal and after regular use, a substantial portion of these active substances (micropollutants) are inevitably entering the aquatic environment.
Pharmaceuticals are one of the most important classes of emerging contaminants in water treatment processes and has direct impact on the human health and the ecosystem. The sources of pharmaceuticals include livestock residues, hospital discharge, aquaculture and release from domestic and industry wastewater effluents. Among them, treatment of wastewaters has become increasingly difficult due to several reasons, including:
- Discharged wastewater contains clusters of micro-pollutants (i.e. pharmaceutical active substance) that are resistant to biological wastewater treatment processes. This is due to the complex molecular structures of these compunds.
- Stringent regulations on effluent discharge limits
Untreated, pharmaceutical residues promote the emerging problems of antibiotic resistant bacterial strains.
In the following text, a few central pharmaceutical compounds will be highlighted to serve as examples for general pharmaceutical residues treatment. These include: paracetamol, codeine, diclofenac, and propofol.
Paracetamol (N-acetyl-4-aminophenol) is a group of medicines (e.g. Alvedon) found in mild analgesics or non-steroidal anti-inflammatory drugs that are sold in large quantities. They are commonly used for reduction of pain and fever symptoms. The projected annual world production of paracetamol is about 145,000 tons. The paracetamol molecule consists of a benzene ring core, substituted by one hydroxyl group and the nitrogen atom of an acetamide. More info about the paracetamol degradation with ozone treatment can be found below.
Codeine (3-Methylmorphine) is a narcotic medication (e.g. Oramorph) used to treat moderate pain and cough. It consists of an aromatic ring and a quaternary carbon atom linked to a tertiary amine group by two other carbon atoms. This chemical characteristic is also known as the morphine rule. The molecule consists of a total of five rings, out of which three are in the same plane.
Diclofenac 2-(2, 6-dichloranillino) phenylacetic acid is a non-steroidal anti-inflammatory drug (i.e. Voltaren) that is easily available in medical outlets and hundreds of tons are sold worldwide every year. It consists of two adjacent aromatic rings, with one ring bearing a carboxylate and the other one, a phenyl ring, binds perpendicular to the top of aromatic ring with two ortho-chloro groups.
Propofol (2,6-Bis(1-methylethyl)phenol) is a stable molecule and an intravenous anesthetic agent used in maintenance of general anesthesia (e.g. Propoven). Propofol consists of a benzene ring and an isopropyl group. Propofol, like the other compounds mentioned above, is effectively degraded to below detection levels with ozone treatment. Propofol in particular has shown a first order reaction in type in a typical wastewater effluent from pharmaceutical industry.
The above pharmaceuticals are complex molecules which are not easily treated in traditional municipal and industrial biological treatment plants.
Overview of additional pharmaceutical residues
Commonly found active micropollutants in wastewater effluents
List of pharmaceutical compounds
Mode of action
Paracetamol degradation example
In-house designed pilot-scale tests demonstrated ›99 % removal of paracetamol directly from a pharmaceutical production plant effluent with optimum concentration of ozone dose. One pathway for paracetamol degradation during the treament process with ozone is hydroxyl radical attack on the aromatic ring with subsequent hydroxylation. Pharmaceutical compounds has a reaction rate that is directly dependent on the concentration of active substance present in the mixture. A schematic figure is presented below where the oxidation pathway and a reaction order representation is displayed.
Overview of Reaction Order
There are different kinds of chemical reactions. The order for any chemical reaction is defined as the reaction rate dependency of the concentration of the reactants. Representative graphs for the 1st, 2nd, and 3rd reaction orders are displayed below:
It is important to determine the reaction kinetics in order to scale a full-scale ozone treatment system. Ozonetech offers pilot project services to determine the specific treatment requirements for specific wastewater streams, including pharmaceutical plants and hospitals wastewater. Contact us for more information!